I can't help but feel that something is missing from the Mercury-Pluto aspect interpretation. The operations of mind are delineated clearly but not its transmission of contents, not the way the Mercury-Pluto individual communicates with his world. And, since a principle need of Mercury is to give voice to ideas, this is an important element to address.

Ebertin in The Combination of Stellar Influneces, is a good supplemental resource in this respect. His thoughts are as follows:

A convincing speaker, the power to influence the public or the masses, a critic, a writer

On the other, less positive side he goes on to say that Mercury/Pluto combinations can also produce,

A plagiarist or a demagogue, in short, persons who are guilty of fraudulent representation or misrepresentation in speaking or writing

As well as,

Hasty thinking and speaking, premature action or hastiness, the spirit of opposition

In short, Mercury/Pluto combinations seem to produce a persuasive bent in the manners of speaking, as well as the occasional mistep into dishonesty.

In addition, and though this is purely theoretic, a tendency with aspects to Pluto is for the needs of the conjoining planet to operate in a mode of "all of mothing," and I this might possibly be the case with Mercury/Pluto combinations as well. Which is to say that the Mercury/Pluto might simply have a tendency toward talking way too much or not at all.

Thoughts on people with this aspect as well as on all I've given here are warmly welcome, let's start a discussion

Good eye. I hadn't particularly noticed that my standard paragraph on Mercury-Pluto doesn't mention communication style. I think it was so obvious to me within the context on how the Me-Pl mind works, that it never occurred to me to say anything about it.

(Minor note: I corrected you Mercury/Pluto to Mercury-Pluto throughout your post. The punctuation is quite precise: The slash is used specifically to designate a midpoint, whereas a hyphen is used for an aspect. Mercury/Pluto means the midpoint of Mercury and Pluto, whereas Mercury-Pluto means the aspect of Mercury and Pluto.)

OTOH, Pluto is the one planet for which I don't trust Ebertin at all. He sometimes gets things right and most often blows it. For example, anytime you see a POWER theme as a trait of Pluto in an Ebertin interpretation, be really suspicious of it! It's there (in a mild form) in his basic Mercury-Pluto principle, "the gift of persuasion" (i.e., power through speech) and spelled out in detail in passages such as you quote. I generally advise people (especially in the learning stage) not to read anything in Ebertin that involves Pluto.

I'll generate a data base of Mercury-Pluto people I know and take a new look at whether to say something specific about their communication style. (Wow, such a stubbornness in myself... as I write that last sentence, I already hear the voice rising up in side me, "But it's inherent in their mental style! What are you talking about, it's already obvious. They communicate like a person whose thinking is individual, unusual, and outlier, perhaps branching to bizarre, little explored topics, like someone who thinks deeply about things, skirts the cliff-edge of normalcy, and is acutely enthusiastic and impatient." LOL.)

First impression from a list of people I know well with Mercury and Pluto in close conjunction, opposition, or square:

As I look at the list, I continue to be drawn back not to their mode of communication but to how their mind works. For example, somewhere near half can be blunt and forthright in what they say, and the other roughly half tend to be unusually quiet (not exactly the "all or nothing," but at least having two varieties.) The diversification on this is so present that, just scanning the list, my first impression is that there is no particular consistent style of expression.

There is, however, a consistent pattern of thought. For example, they all have acute ideas that mean a great deal to them. Some insistently speak up, some graciously speak up, some hover in the background abiding in being unheard, but they all seem to be bursting with the intensity of their ideas like an adolescent male's impatient tumescence.

Given this, I think there probably is a vulnerability to feeling unheard. (I have to look at what the charts have in common.) This may be from the rest of their charts, e.g., three of the four most extreme examples of this are all Leo Suns (and a fourth is an Aries - not you, of course). For these three, it really seems they feel they have a royal prerogative to be heard and for people to align with what they say, a sense that they have the royal-born right to have people treat them as the authority. But is this Leo Sun, Mercury-Pluto, or (most likely) a blend?

I hope Freya notices this thread and jumps in. She has a 0°11' Mercury-Pluto square in the immediate background plus double Mercurial luminaries. In trying to keep my thoughts about style of communication more than style of thought where possible, I observe her as deeply thinking things through that having something quite decisive to say and saying it. She is inherently gracious and finds no conflict between manners and bluntness. Being a woman and European, and having had more than a little struggle in life, I'm sure she has spent much of her life feeling nobody is listening to her (probably because nobody was listening to a woman), though this could be shown by the background Mercury alone. Nonetheless, she has found her voice and speaks freely.

coolcoolwcr is quite different. He strikes me as demanding attention to what he has to say and to exercise dominion through it. This, though, is consistent with his Aries luminaries alone. His Mercury is in Aries, opposite Pluto 0°37' in the middleground.

Another friend (a Taurus-Virgo with a partile background Mercury-Pluto square) is indeed marked by unhesitant to speak up. He "speaks truth to power" graciously at the personal level, but loudly and intolerantly as an activist. Communication is important to him - he probably had a hard time moving off the idea he was a TZ Gemini - and he exercises this through the arts and activism. I value that I can always take what he says as reflecting what he really thinks and where he's really coming from. (This is probably a general trait of Mercury-Pluto, probably spinning out of the need for authenticity in communication.)

Another friend with a background close Mercury-Pluto square is most marked by thinking his own thoughts and having his own opinions even amidst groups where they are unpopular or minority opinions, and being willing to express them or not as the listener is open to them. But then, he's an Aquarius, so a lot of these traits are natural to his Sun-sign. He is involved in mental minutia professionally, his intellect usually dominates his thinking processes, and he usually has things deeply thought through.

Another person is a Leo with a number of arrogant, vain markers in his chart. Mercury conjoins Pluto (Class 1) in the middleground. He was always an obnoxious prick dominating conversations (in the "I have to get my say in so that people will know I'm smart" kind of way). Honestly inquiring, with a research bent, and sincere in his pursuit of knowledge, but pretty alienating to most people in his communication.

Two more Leos in a row that always seemed pretty bumped that their authority was insufficient and disdainful of people who didn't agree with them. One has Mercury conjunct Pluto in the middleground with Sun-Neptune and Mars-Saturn angular. The other has a foreground Mercury-Pluto conjunction (with Venus) plus an angular Sun. Their typical communication styles were quite different.

A double Spoke with a background partile Mercury-Pluto opposition was an incredible researcher and an incredible eager-beaver to share his discoveries. Quite animated and eager (eager is the best word for him all 'round!) to get people to listen to him and his discoveries.

One of the most obnoxious people I've ever known was a Pisces-Taurus (Saturn rising) with a close background Mercury-Pluto opposition. She was untrustworthy, deceptive, vindictive, passionate about her rather narrow point of view and extremely reactive to anyone who wouldn't align with her opinions.

An Aries-Aquarius is one of the gentlest, most mindful young people I've known. Mercury closely opposes Pluto with Pluto foreground and Mercury middleground. (The Aries Sun is partile opposite Pluto, even closer than Mercury.) Inquiring mind, willing to conceive life outside the box, etc.

Another Aquarius, this time with a Virgo Moon, has a middleground Mercury-Pluto opposition. She was a writer on outlier subjects, sometimes an investigative reporter, intellectually brilliant and particularly quick. Her communication style always seemed more filtered to me than I expect from Mercury-Pluto or Aquarius Sun, as if it were coming through a Jupiter filter - it isn't - though ultimately she is pretty candid.

As I have time, I'll come back and see if I can discern any commonalities in these. In writing them, on and off during the day, my general impression was that the Mercury-Pluto was quite basic and the underlying character - especially the Sun-sign - was often front and center in how this aspect was expressed. I also noticed that there are so many background Mercuries that I have to be careful in assuming that any constraint from communication or feeling unheard comes from the aspect instead of just the background Mercury itself.

Based on this, I have a possible (tentative) rewrite of the Mercury-Pluto paragraph. I'll post it here as a possible new starting point for continuing this very Mercury-Pluto like inquiry that the OP began.

I dont have this aspect in my natal, however if it's worth anything I do have a close trine between the two in my novile chart. I have to say that I also have a large Leo influence (in the Moon), however this is truly pummeled back by my Pluto Moon square.

I also have a Venus Moon undertone, ie moon Is in a Venus of Venus place (making for a highly emotional place, made extreme by Pluto, which is may be matched by my Sun-Venus in cancer in my novile chart) but I dont have any Mercury Moon connection.

For me my childhood was an emotional one (likely very Pluto-Venus and perhaps Saturn heavy) and because I thought I didn't deserve to speak about my feelings/feelings make you seem vulnerable I was actually mute.

I do think that the Pluto-Mercury mind sits as Geminiesc and is highly Anti-Jupiter which is what causes a thinking and speech style that is against traditional practices, ie that once they (Pluto-Mercury folks) realize that the words Jim has used to sum up the aspect has become to systematically true, they will find a way to throw a wrench in the cog.

I like to think of Pluto-Mercury thinking as each thought is a little amylopectin (branched starch molecule) so each thought has tiny sub thoughts, and those sub thoughts easily connect to other thoughts which also have sub thoughts more so that most other people in society who think in a amylose (unbranched starch molecule) way.

I have a natal sextile class one Mercury-Pluto and I like what was written that the native has a clear belief in thought, whatever it maybe, and needs to be expressed or voiced out loud. And it comes out confidently, persuasive to others in the authentic delivery. Also, the deep contemplation of things. I personally play out communication like a chess match in my mind about the nature of things. I also enjoy structuring music when I play. In bands, I had to direct everything. When intoxicated with pot and/or thinking clearly, I can be very candid about what I think, and it usually comes off curious. It sparks others to ask questions of what I mean.